**Core Concept**
Quinolones are a class of broad-spectrum antibacterial antibiotics that inhibit bacterial DNA replication. However, their use in lactating mothers is limited due to potential effects on the infant's developing cartilage and bone. This is because quinolones can inhibit the enzyme isopentenyl transferase, which is essential for the synthesis of isoprenoids, precursors to cholesterol.

**Why the Correct Answer is Right**
Quinolones are not recommended for lactating mothers because they can be excreted in breast milk and may cause cartilage damage to the infant's developing bones. This is a concern because quinolones can inhibit the synthesis of isopentenyl pyrophosphate, a precursor to cholesterol and other isoprenoids, which are essential for bone growth and development. The use of quinolones in lactating mothers may lead to arthropathy or other bone-related issues in the infant.

**Why Each Wrong Option is Incorrect**
**Option A:** Cephalosporins are generally considered safe for use in lactating mothers, as they are excreted in small amounts in breast milk and do not appear to cause harm to the infant.
**Option B:** Anti-tubercular drugs, such as isoniazid and rifampicin, are often used in lactating mothers to treat tuberculosis, as the benefits of treatment outweigh the potential risks to the infant.
**Option D:** Aminoglycosides, such as gentamicin and tobramycin, are not typically used in lactating mothers due to their potential to cause nephrotoxicity and ototoxicity in the infant, rather than their effect on bone growth.

**Clinical Pearl / High-Yield Fact**
When prescribing antibacterial antibiotics to lactating mothers, it is essential to weigh the benefits of treatment against the potential risks to the infant. Quinolones should be avoided in lactating mothers due to their potential to cause cartilage damage and other bone-related issues in the infant.

**✓ Correct Answer: C. Quinolones**